As a long-time reef aquarium hobbyist, I’ve seen lighting options change over the decades. Early reports from Europe in the late 1980’s suggested use of full spectrum fluorescent lamps, followed by reports of success through use of actinic blue lights. Variations of fluorescent lamps (high output, very high output, compact fluorescent, T5, etc.) have been used with good results as have metal halide lamps of various Kelvin ratings. PFO Lighting revolutionized aquarium lighting when they introduced LED luminaires in about 2005. Today, LED arrays have largely (not completely) replaced other lighting options and for good reasons – light intensity can rival that of just about any competing light source, the lamps (diodes) are long-lived and maintain their color temperature over extended periods of time, heat transfer is reasonable and usually doesn’t require a chiller, energy consumption compared to light output is generally good, and, perhaps most importantly, we can avoid ‘light shock’ to corals and other photosynthetic invertebrates that can potentially happen when aged fluorescent or metal halide lamps are replaced with new ones. Some LED luminaires allow the user to program light intensity/color to ramp up or down during the photoperiod (also programmable.) It is for these reasons that I use LED fixtures.

This month, we’ll examine a LED luminaire that offers these options – Kessil’s AP700. This luminaire has two LED ‘pucks’ or, more correctly, two lights each containing dozens of light-emitting diodes (Kessil calls them ‘Dense Matrix’ LEDs.) Many of these diodes possess distinct spectral characteristics. Independent LED channels allows spectral tuning, either through use of user-specified or nine preprogrammed settings and can provide light ranging from violet/blue to a crisp blue-white light.


Advertisements tout this luminaire’s superior light production, adjustable color output, and ‘perfect’ and ‘maximum coverage.’ How do these claims hold up under scrutiny?

Dimensions and Other Specifications

  • Length: 20.25″
  • Width: 6.25″
  • Height: 1.5″
  • Number of LED Pucks: 2
  • Cord Length (total, approximate): 16′
  • Cord Length (Outlet to Rectifier): 10′
  • Cord Length (Rectifier to Fixture): 6′


    Power Consumption

    Kessil advertises the AP700 to consume a maximum 185 watts of power. I found the test unit to use a maximum of 161 watts. See Figure 1.


    Figure 1. This luminaire consumes the most power when set to the ‘bluest’ setting, although it is below the advertised 185 watts.

    Light Intensity

    Reporting light intensities generated by this unit presents many challenges. First, the luminaire’s keypad offers selection of 9 preset intensity settings. In addition, it became apparent very quickly that different spectral quality settings also influenced intensity. Instead of checking intensity at each setting combination, I decided to present intensities as measured at the highest intensity setting at each spectral setting. These measurements were made by the latest PAR (quantum) meter iteration from Apogee Instruments – the MQ-510. See Figure 2 for these measurements.


    Figure 2. PAR measurements at the nine preset spectral settings offered by the Kessil AP700. These measurements are for illustrative purposes only and demonstrate how light intensity changes among settings.

    Light Intensity at Depth

    Again, the almost infinite number of user selected options make reporting of light intensity at various depths a daunting task. It was decided to report those settings that generated the most, and least, PAR (and as it turned out – PUR as well) at depths of 17″, 13″, 7.5″, and 3″. The least amount of PAR (and PUR) were generated at the ‘whitest’ (least blue) setting while the most was produced at the #2 setting (#1 being bluest.)

    The fixture was mounted 6″ above the water surface. See Figures 3 through 10.


    Figure 3. This setting generated the least amount of PAR.


    Figure 4. Setting #2 generated the most PAR and PUR.


    Figure 5. PAR measurements at a depth of 13 inches.


    Figure 6. Pay close attention to the PAR increments in the legend.


    Figure 7. The intersection of light fields from the two LED pucks creates a hotspot.


    Figure 8. PAR measurements at a depth of 7.5 inches.


    Figure 9. PAR values at a depth of 3 inches. The ‘whitest’ setting created the least amount of PAR of any setting.


    Figure 10. PAR at a depth of 3 inches.

    Spectral Settings

    The Kessil AP700 offers the option of 9 preset spectral settings, ranging from ‘very blue’ to ‘blue-white’ (my terms, not Kessil’s.) See Figure 11.


    Figure 11. Ultraviolet, violet, and blue wavelengths are dominant at the ‘bluest’ setting with longer wavelengths increasing as the lamps become ‘whiter.’

    Further analyses give us a good idea of the spectral quality at each setting. The ‘bluest’ setting is self-explanatory, setting #2 is slightly less blue and more of a broad spectrum, and so on until we arrive at the ‘whitest’ setting. We’ll start at:

    Bluest Setting

    As expected, the ‘bluest’ spectral setting generated the most UV-A, violet and blue light, and the least amount of warmer spectra. See Figures 12 and 13.


    Figure 12. Spectral composition of the ‘bluest’ setting.


    Figure 13. Spectral characteristics (10 nm bandwidths) of the ‘bluest’ setting.

    Setting #2: This setting produced the most PAR. See Figures 14 and 15.


    Figure 14. Spectral characteristics of Setting #2.


    Figure 15. An Ocean Optics spectrometer determined spectral qualities.

    Setting #3: The light generated by the Kessil AP700 becomes warmer at Setting #3. See Figures 16 and 17.


    Figure 16. Setting #3 produces less cool colors.


    Figure 17. Warmer colors are apparent at Setting #3.

    Setting 4: As would be expected, blue light decreases as warmer colors increase. See Figures 18 and 19.


    Figure 18. Spectral composition at Setting #4.


    Figure 19. Setting #4 spectral intensities at 10nm increments.

    Setting #5: Figures 20 and 21 demonstrate spectral qualities at the #5 preprogrammed setting.


    Figure 20. Spectral composition of Setting #5.


    Figure 21. Note that very little UV-A radiation is produced at this setting. See below.

    Setting #6: As expected, this preprogrammed setting becomes warmer in color temperature. See Figures 22 and 23.


    Figure 22. Spectral quality becomes warmer at Setting #6.


    Figure 23. Setting #6.

    Setting #7: This setting generates a crisp blue-white light and should showcase the colors of fishes with yellow-red markings. See Figures 24 and 25.


    Figure 24. Although light at Setting #7 is warmer, violet and blue light is still greater than 50%.


    Figure 25. Spectral composition of light at Setting #7.

    Setting #8: This setting might be a good choice for those aquarists not fond of the blue ‘Windex’ look. See Figures 26 and 27.


    Figure 26. Blue light is still a major component at Setting #8.


    Figure 27. Spectral characteristics of Setting #8 at 10nm bandwidths.

    ‘Whitest’ Setting: This setting produces the warmest wavelengths. See Figures 28 and 29.


    Figure 28. This pie chart shows the spectral composition of the ‘warmest’ setting.


    Figure 29. A proprietary Excel program determined these spectral characteristics.

    Photosynthetically Usable Radiation (PUR)

    Although all wavelengths between 389 and 692nm (with caveats) are reported more or less equally by the meter used to test PAR (Apogee’s MQ-510), that does not mean these wavelengths promote photosynthesis equally and we should be more interested in photosynthetically usable radiation (PUR.) To this end, PUR was estimated through use of a Seneye Reef monitor. Seneye informed me that PUR is calculated by using coefficients based on light absorption of zooxanthellae. There are many ways to calculate PUR and all have their advantages and disadvantages. Figure 30 shows PUR estimations at various spectral settings.


    Figure 30. Photosynthetically Usable Radiation (PUR) at the pre-programmed settings.

    However, PUR estimations do not tell the full story as intensity at each setting must be considered. Figure 31 shows the estimated PUR rating when we multiply the PAR measurement made at each setting when multiplied by the percentage of PUR of each measurement.


    Figure 31. PUR, in and of itself, doesn’t tell the whole story. When we multiply the PAR measurement by % PUR generated, we arrive at a rating for the 9 pre-programmed settings.

    Ultraviolet Radiation

    Ultraviolet radiation generated by this fixture falls into the UV-A range with wavelengths of about 380nm to 400nm. Years ago, it was widely believed that UV-A was responsible for inducing coral coloration. Since, it has been proven that many fluorescent and non-fluorescent proteins (chromo-proteins) are made in response to violet/blue wavelengths. However, UV-A in the range made by this fixture can promote photosynthesis, and its presence should not be discounted.

    Kessil states that UV is produced regardless of the color setting. While true, analysis through spectroscopy reveals production of UV-A falls as the spectrum shifts towards warmer wavelengths. See Figure 32.


    Figure 32. Ultraviolet-A production (as a percent of total radiation between 365nm and 700n) by the Kessil AP700. Setting #1 is ‘most blue’ while Setting #9 is ‘least blue’. Measurements made by an Ocean Optics spectrometer.

    Heat Production

    All lighting systems produce some heat as a waste by-product. This Kessil luminaire is no exception. I learned the hard way that heat generated is sufficient to melt eggcrate material. See Figure 33. If you use this option for supporting the luminaire above the aquarium, it is advisable to cut eggcrate away from directly below the LED pucks.


    Figure 33. Placing the AP700 directly upon eggcrate material is probably not a good idea. Note that the lamp, when mounted 6″ above the water line, did not add heat to the aquarium. The grids outlined in black were later used for repeatable positioning of the quantum meter sensor during testing.

    Mounting Hardware

    This hardware is not included with the luminaire and is available as an option. The less expensive mounting kit consists of stainless steel bolts, wire and toggle bolts that allow a ceiling mount. I used this option, and it took about 15 minutes to complete the job, including drilling holes in the suspended ceiling (the luminaire is light weight -about 4 pounds- and should present no issues if the ceiling tiles are heavy duty (2’x2′ and rated for damp environments. Bracing may be required for inexpensive 2’x 4′ tiles.) The other option is mounting rails that affix to the back of the aquarium (or stand) – two of these rails are required for the AP700.

    If the luminaire is to be mounted within a canopy, it should be noted that the standard mounting cables will place the bottom of the luminaire about 11″ below the inside top of the canopy. In other words, you’ll need about 12″ of space from the inside top of the canopy to the top of the aquarium. It is possible this requirement could lessen if the cable system is modified by the end user.

    Testing Protocol

    The luminaire was suspended six inches above a 120- gallon aquarium (48″ x 24″ x 24″. See Figure 34.) Plastic eggcrate material was cut to fit within the aquarium and used as a grid system. Squares within this grid were marked every four inches with a black Sharpie. The sensor of an Apogee MQ-510 quantum sensor had a coral frag plug attached via magnets and measured photosynthetically active radiation (PAR.) This allowed the sensor to be placed in repeatable positions at all depths tested.


    Figure 34. The Kessil AP700 mounted above the 120-gallon aquarium used for testing. This stainless steel cable suspension system is optional at a cost of about $40.

    The Apogee MQ-510 meter is designed specifically for aquarium use. Sensor response rages from UV-A (389nm) to red (692 nm), ± 5 nm where response is greater than 50% of maximum. See Figure 35.


    Figure 35. Apogee Instruments’ fine little quantum (PAR) meter and improved sensor. Every hobbyist should own some sort of light-measuring device.

    Photosynthetically Usable Radiation (PUR) was estimated through use of a Seneye Reef sensor.

    Spectral characteristics were measured by an Ocean Optics USB 2000 spectrometer using a 400-micron diameter fiber optic patch cord and OOI’s OceanView software. Results were exported to MS Excel for analyses through a proprietary program and charted.

    Electrical consumption was measured by a P3 International Kill-A-Watt meter.


    Kessil’s programming has a number of options available including ‘red moonlight’, ‘blue moonlight’, ‘aurora,’ ‘rainbow’, ‘weather’ settings, ‘acclimation’ and so forth. Used defined settings are also possible.

    Using this feature is straight-forward. Go to www.kessil.com and download appropriate software for iOS or Android. Once installed, open the app and it will walk you through the process.

    Manufacturer’s Suggested Retail Price

    MSRP is $895.00 US, plus sales tax and shipping, if applicable. However, a little searching on the internet found a price of $799.00 US.

    The stainless steel cable suspension system is an option priced at $40. Another option consists of two arms that attach to the aquarium. These are $65 each, for a total of $130.


    Kessil guarantees this product for a period of 12 months.


    It has always been my opinion that there are no poor lighting systems (within reason, of course) but there are poor applications. Does the Kessil AP700 have the capability of promoting photosynthesis? Of course, it can. Can it induce coral coloration if the coral is genetically predisposed to do so in response to light? Quite possible. So, the question becomes that of proper application.

    Kessil makes recommendations that, in my opinion, fell short under the conditions of testing described here. For instance, their website states the AP700 should be mounted 5″-7″ above the water line of a SPS-dominated reef for an area coverage of 36 inches by 24 inches. For ‘mixed reefs’ (I assume this means a mix of stony and soft corals) Kessil recommends a height of 15-18″ above the water. Further, it is stated the latter coverage is achievable for most reefs (definition needed!) at depths of 24 to 30 inches.

    To evaluate these claims, we must define a minimum amount of light needed for photosynthesis to proceed at a sufficient rate. In general, a PAR value of about 100 µmol·m²·sec will meet the minimum lighting requirements of many corals. Certainly, some corals can live at a lesser intensity, but 100 µmol·m²·sec gives a comfort zone to most corals (and hobbyists!) The aquarist using this Kessil should be selective in placing stony corals in areas of light intensity less than 100 µmol·m²·sec.

    At the ‘whitest’ setting, there was an area 16″ long (1/3 of the aquarium length) that exceeded 100 µmol·m²·sec at a depth of 17 inches. At the most intense setting (#2) there was an area 24″ that exceeded 100 µmol·m²·sec. I’ll let you review the PAR measurement figures for details.

    There are many things I like about this light. The spectral quality of the #2 setting is most appealing to my eye – it is a crisp blue-white, reminding me of some of the 14,000K metal halide lamps. This setting also promotes nice fluorescence in some of the corals. See Figure 36. The LED ‘pucks’ act as point source lights (much as metal halide lamps do) and create a nice caustic network (an evil sounding, but technically correct, name for what is variously called ‘glitter lines’, ‘shimmer’, ‘flicker’, etc.) There is no ‘disco effect’ as the color mixing is superb.


    Figure 36. The spectral quality of the AP 700 is adjustable and can be fine-tuned to showcase fluorescence, as in this young Euphyllia specimen.

    To be fair, there are some things I’m not particularly fond of as well. Perhaps I’m just old fashioned, but control of light intensity/spectral qualities from your smart phone or computer is an invitation to play with these parameters – something your corals might not appreciate. There are some who don’t have access to devices required to adjust the outputs, or perhaps don’t care to expend the effort to learn how to effectively use these. I think there is a lesson to learn from the built-in programming of the Chinese ‘black boxes’ – some of these luminaires offer a timer and spectral adjustments through use of an onboard keypad. In addition, the programming in this Kessil model offers options such as ‘rainbow’, ‘storm’, etc., probably to increase the ‘wow factor’ during the sales pitch, but I suspect few will utilize some of the options. And a pet peeve – a lunar cycle is one of those options of limited utility. It is a common misconception that moonlight is a major factor in timing coral spawning (it isn’t – it is the length of photoperiod for many coral species. But that is a different story for another time.)

    In closing, the Kessil AP700 appears to be well built and has many features that make it appealing. I am now using one of these luminaires over my display aquarium (mounted about 2″ above the water surface and a setting of #2 for maximum PUR) and am impressed with the color mixing and spectral characteristics, especially with some of the corals displaying fluorescence. It is not inexpensive (as lights in this class tend to be.) A careful review of information presented here might help determine if this luminaire is right for you.


    The author wishes to thank Matt at Boom Corals (www.boomcorals.com) for financial support in obtaining this fixture. Tullio Dellaquila of Reef Brite (www.reefbrite.com) kindly donated the Seneye Reef monitor.

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